Pitch Black was totally sci-fi, because it required me to suspend my disbelief on an important plot point: That a species of high-speed, giant, carnivorous, predatory bats could survive for eons on a planet with little to no prey to feed upon, and then pour out of the caves in vast numbers just because of an eclipse, to feed upon a scant handful of humans who were there more or less by accident. Surely some kind of science fiction has to be happening for a species to be able to survive and propogate in those circumstances.